Mac PBE won't open

Yesterday I was accepted to the PBE group and naturally being excited to contribute to the working of the game I wanted to download the client and start playing. Although it's quite difficult to find where to actually download the PBE client the bigger problem is that whenever I open it, it sits in my hotbar and will bounce up and down endlessly not actually doing anything. I've tried redownloading and fixing the files but nothing has seemed to work. I hope you can get back. Thank you for your time!